The disadvantages encountered in certain types of polymerization procedures, viz., difficult heat control in bulk polymerization, and the low molecular weight products, slow reaction, and product impurity due to the presence of traces of solvents in solution polymerization, are all successfully overcome by suspension polymerization in an aqueous medium. Notwithstanding these advantages, many polymers, such as the long hydrocarbon chain containing polyacrylates, or vinylesters etc. having low Tg (i.e. second order transition temperature), e.g. below -45.degree. C. have not been prepared in this manner for the reason that droplets of their respective monomers collapse upon contact and agglomerate in a large mass which prevents heat removal and terminates the polymerization. This effect with monomers having a Tg less than -45.degree. C. is not avoided by high mechanical agitation or by the use of suspension aids since the walls of the droplets are not sufficiently strong to withstand normal impact. For this reason, monomers of low Tg have been reacted by bulk, solution or emulsion methods when polymerization is desired. The presence of emulsifiers and other chemicals in the reaction mixture produces a less desirable product since the small amounts of such ingredients necessary for a successful course of reaction are occluded inside the agglomerated polymer and can not be easily removed by the best of washing procedures. The only way to obtain pure polymer product formed by such processes involves repeated dissolution and reprecipitation of the coagulated product, which procedure is not economically feasible in industrial operations.
Accordingly, it is an object of the present invention to provide a method for polymerizing monomers having a low Tg by the suspension method in a unique aqueous suspension medium.
It is another object of the present invention to provide an economic and commercially feasible process for obtaining high molecular weight polymers of low Tg monomers.
Another object of this invention is to simultaneously produce separate and distinct homopolymers of organophilic and hydrophilic monomers in a high state of purity.
Another object is to provide a suspension polymerization process which achieves economical separation and recovery of the simultaneously produced organophilic and hydrophilic homopolymers.
These and other objects of this invention will become apparent from the following description and disclosure.